The relationship between the percentage of lung shunting on Tc-99m macroaggregated albumin (Tc-99m MAA) scan and the grade of hepatocellular carcinoma vascularity

Background

Hepatocellular carcinoma (HCC) stands for the majority of primary liver malignancy. HCC has variable grade of vascularity according to the histological tumor grade and underlying liver damage. Yttrium-90 radioembolization is a promising catheter-based hepatic intra-arterial therapy for HCC that necessitates proper planning. Technetium-99m macroaggregated albumin (Tc-99m MAA), a simulation of the treatment, is used to identify the shunting of microspheres to the lungs or gastrointestinal tract.

Objective

To evaluate the relationship between the percentage of lung shunting on Tc-99m MAA scan performed in treatment planning of Yttrium-90 (Y-90) microsphere selective internal radiation therapy (SIRT) for HCC and the grade of tumor vascularity shown on digital subtraction hepatic angiography.

Materials and methods

This study was conducted on 19 patients diagnosed to have HCC, based on typical computed tomography (CT) criteria and/or elevated alpha-fetoprotein (AFP) ?200 ng/ml, and planned for Y-90 therapy. They were injected by Tc-99m MAA into the hepatic arterial territory with prior digital subtraction angiography. Tc-99m MAA scan was reviewed for extrahepatic shunting within the abdomen. Additionally, the hepatopulmonary shunt (HPS) fraction or the lung shunting (LS) percentage was calculated and further evaluated in relation to the grade of tumor vascularity shown on digital subtraction hepatic angiography.

Results

There was no extrahepatic accumulation of Tc-99m MAA related to umbilical, gastroduodenal or splenic shunting. The LS percentage assorted among patients and ranged between 0.8% and 42.9% with a median of 5.5%. LS more than 20% occurred in only 1 patient. Subsequent therapy plan was changed accordingly in 5% of patients. The more vascular the lesion was, the higher lung shunting percentage was detected.

Conclusion

Tc-99m MAA scan is fundamental prior to Y-90 microsphere SIRT as it minimizes the risk of post-radioembolization complications, hence, enhancing the safety of Y-90 microsphere subsequent administration. Moreover, the percentage of lung shunting varies considerably among patients with HCC relying on the grade of tumor vascularity.